Urea-containing mercaptosilanes, process for preparation thereof and use thereof

ABSTRACT

The invention relates to urea-containing mercaptosilanes of the formula I 
                         
which are prepared by reacting a halosilane of the formula II
 
                         
with compounds of the formula III
 
                         
in an alcohol.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority to German Application No. 102014209233.7, filed on May 15, 2014, the disclosure of which is incorporated by reference herein in its entirety, and priority to which is hereby claimed.

The invention relates to urea-containing mercaptosilanes, to processes for preparation thereof and to the use thereof.

CAS 1082204-82-7, 1268617-33-9 and 104261-54-3 disclose compounds of the formula

In addition, JP 2008279736 A discloses urea-containing silanes for coatings.

DE 3424534 A1 discloses N,N′- and N,N′,N′-substituted urea-containing silanes of the formula

The preparation is effected by reacting an amino compound, a halosilane and alkali metal cyanate in an aprotic polar organic solvent, for example DMF or DMSO.

In addition, JP 2002311574 discloses powder coatings comprising silanes of the formula R¹—S—R²—NH—C(O)—NH—R³—Si(R⁴)_(m)(OR⁵)_(3-m).

WO 9955754 A1 discloses photosensitive resin compositions comprising alkoxysilanes of the formula [(R¹O)_(3-a)(R²)_(a)Si—R³-A-C(O)—B]_(m)—X.

Disadvantages of the known urea-containing mercaptosilanes are poor processing characteristics, low network density, poor wet skid properties and low dynamic stiffness.

It is an object of the present invention to provide urea-containing mercaptosilanes having improved processing characteristics, network density, wet skid properties and dynamic stiffness in rubber mixtures compared to urea-containing mercaptosilanes known from the prior art.

The invention provides a urea-containing mercaptosilane of the formula I

where R¹ are the same or different and are C1-C10 alkoxy groups, preferably methoxy or ethoxy group, C2-C10 cyclic dialkoxy groups, phenoxy group, C4-C10 cycloalkoxy groups, C6-C20 aryl groups, preferably phenyl, C1-C10 alkyl groups, preferably methyl or ethyl, C2-C20 alkenyl group, C7-C20 aralkyl group or halogen, preferably Cl, R² is a monovalent C1-C20 hydrocarbon group, preferably a C1-C20 alkyl group, C6-C20 aryl group, C2-C20 alkenyl group or C7-C20 aralkyl group, and R are the same or different and are a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C₁-C₃₀, preferably C₁-C₂₀, more preferably C₁-C₁₀, even more preferably C₁-C₇, especially preferably C₂ and C₃, hydrocarbon group optionally substituted by F—, Cl—, Br—, I—, —CN or HS—.

Urea-containing mercaptosilanes may be mixtures of urea-containing mercaptosilanes of the formula I.

The process product may comprise oligomers which form through hydrolysis and condensation of the alkoxysilane functions of the urea-containing mercaptosilanes of the formula I.

The urea-containing mercaptosilanes of the formula I may be applied to a support, for example wax, polymer or carbon black. The urea-containing mercaptosilanes of the formula I may be applied to a silica, in which case the binding may be physical or chemical.

R may preferably be

-   -   —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)—,         —CH₂CH(CH₃)—, —CH(CH₃)CH₂—, —C(CH₃)₂—, —CH(C₂H₅)—,         —CH₂CH₂CH(CH₃)—, —CH(CH₃)CH₂CH₂—,     -   —CH₂CH(CH₃)CH₂—, —CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂—,     -   —CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,     -   CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,         —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,         —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,         —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—,         —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—         -   or

R¹ may preferably be methoxy or ethoxy.

R² may preferably be CH₃, CH₂CH₃, CH₂CH₂CH₃ oder (CH₂)₆CH₃.

Urea-containing mercaptosilanes of the formula I may preferably be:

-   -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃.

An especially preferred compound is of the formula (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃.

The invention further provides a process for preparing the inventive urea-containing mercaptosilanes of the formula I

where R¹, R² and R are each as defined above, which is characterized in that a halosilane of the formula II

is reacted with a compound of formula III

where R¹, R² and R are each as defined above, Hal is F, Cl, Br or I, preferably Cl, and M is an alkali metal, preferably K or Na, in an alcohol.

Halosilanes of the formula II may preferably be:

-   -   (C₂H₅O)₃Si—CH₂—NH—C(O)—NH—CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (C2H₅O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl,     -   (C₂H₅O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl,     -   (CH₃O)₃Si—CH₂—NH—C(O)—NH—CH₂—Cl,     -   (CH₃O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂—Cl,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂—Cl,     -   (CH₃O)₃Si—CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (CH₃O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂CH₂—Cl,     -   (CH₃O)₃Si—CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl,     -   (CH₃O)₃Si—CH₂CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl or     -   (CH₃O)₃Si—CH₂CH₂CH₂—NH—C(O)—NH—CH₂CH₂CH₂—Cl.         Compounds of the formula III may preferably be:     -   NaS—C(O)—CH₃,     -   NaS—C(O)—CH₂CH₃,     -   NaS—C(O)—CH₂CH₂CH₃,     -   NaS—C(O)—(CH₂)₆CH₃,     -   KS—C(O)—CH₃,     -   KS—C(O)—CH₂CH₃,     -   KS—C(O)—CH₂CH₂CH₃ or     -   KS—C(O)—(CH₂)₆CH₃.

In the process according to the invention, the halosilane of the formula II may be metered into the compound of the formula III.

In the process according to the invention, compound of the formula III may preferably be metered into halosilane of the formula II.

In the process according to the invention, the halosilane of the formula II can be used relative to the compound of the formula III in a molar ratio of 0.85:1 to 1.15:1, preferably 0.90:1 to 1.10:1, more preferably in a ratio of 0.95:1 to 1.05:1.

The reaction can be conducted with exclusion of air.

The reaction may be carried out under a protective gas atmosphere, for example under argon or nitrogen, preferably under nitrogen.

The process of the invention can be carried out at atmospheric pressure, elevated pressure or reduced pressure. Preferably, the process according to the invention can be conducted at standard pressure.

Elevated pressure may be a pressure from 1.1 bar to 100 bar, preferably of 1.5 bar to 50 bar, more preferably of 2 bar to 20 bar and very preferably of 2 to 10 bar.

Reduced pressure may be a pressure of 1 mbar to 1000 mbar, preferably 1 mbar to 500 mbar, more preferably 1 mbar to 250 mbar, very preferably 5 mbar to 100 mbar.

The process according to the invention can be conducted between 0° C. and 150° C., preferably between 20° C. and 100° C., more preferably between 50° C. and 80° C. Especially preferably, the process according to the invention can be conducted at the boiling point of the alcohol.

The alcohol used in the process according to the invention may preferably be methanol, ethanol, propanol, butanol or cyclohexanol. The alcohol may especially preferably be ethanol.

The alcohol can be removed, preferably distilled off, after the reaction.

The reaction product can subsequently be dried. The drying can be effected at temperatures of +20° C.-+100° C., preferably of +25° C.-+75° C. The drying can be effected at a reduced pressure of 1-500 mbar.

The urea-containing mercaptosilane of the formula I obtainable by the process according to the invention

can be obtained in a yield of greater than 50%, preferably greater than 60%, very preferably greater than 70%.

In one embodiment, the halosilane of the formula II, prior to the reaction with the compound of the formula III, can be prepared from the hydrochloride salt of an amine of the formula IV

and isocyanatosilane of the formula V

by addition of a base, preferably NaOEt, where Hal, R¹ and R are each as defined above. The base can be added until a pH between 7 and 14 is established. In the process according to the invention, the hydrochloride salt of the amines of the formula IV can be used relative to isocyanatosilane of the formula V in a molar ratio of 0.85:1 to 1.15:1, preferably 0.90:1 to 1.10:1, more preferably in a ratio of 0.95:1 to 1.05:1.

In the aforementioned embodiment, the process according to the invention for preparing urea-containing mercaptosilanes of the formula I

where R¹, R² and R are each as defined above may be characterized in that the hydrochloride salt of the amine of the formula IV

is dissolved in alcohol and reacted with a base, then the isocyanatosilane of the formula V

is added, and then compounds of the formula III

are added, the mixture is filtered and the solvent is removed, where Hal, M, R¹, R² and R are each as defined above.

In a further embodiment, the halosilane of the formula II, prior to the reaction with the compound of the formula III, can be prepared from the isocyanate-halogen compound of the formula VI

and aminosilane of the formula VII

where Hal, R and R¹ are each as defined above. The reaction can be conducted in a solvent, preferably alcohol, more preferably ethanol.

In the process according to the invention, the isocyanate-halogen compound of the formula VI can be used relative to aminosilane of the formula VII in a molar ratio of 0.85:1 to 1.15:1, preferably 0.90:1 to 1.10:1, more preferably in a ratio of 0.95:1 to 1.05:1.

In the aforementioned embodiment, the process according to the invention for preparing urea-containing mercaptosilanes of the formula I

where R¹, R² and R are each as defined above may be characterized in that an isocyanate-halogen compound of the formula VI

and aminosilane of the formula VII

are reacted in alcohol, preferably ethanol, and then a compound of the formula III

is added, the mixture is filtered and the alcohol is removed, where Hal, M, R, R¹ and R² are each as defined above.

The product prepared by the process according to the invention may have a residual content of halosilane of the formula II of less than 25 mol %, preferably less than 10 mol %, more preferably less than 5 mol %, very preferably less than 3 mol %.

The relative molar percentages of the halosilane of the formula II in the product prepared by the process according to the invention are determined in the ¹H NMR by integration of the hydrogen atoms in the —CH₂CH ₂—Cl group of the halosilane of the formula II against the hydrogen atoms in the Si—CH ₂— group of the urea-containing mercaptosilane of the formula I. For the substance of the formula II (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—Cl, for example, the integral of the hydrogen atoms of the —CH₂CH ₂—Cl group (δ=3.17 ppm) is used for the determination of the relative contents.

The product prepared by the process according to the invention may have a residual content of hydrochloride salt of an amine of the formula IV of less than 25 mol %, preferably less than 10 mol %, more preferably less than 5 mol %, very preferably less than 3 mol %.

The relative molar percentages of the hydrochloride salt of an amine of the formula IV in the product prepared by the process according to the invention are determined in the ¹³C NMR by integration of the carbon atoms in the —CH₂—NH₂.HCl group of the hydrochloride salt of an amine of the formula IV against the carbon atoms in the Si—CH₂— group of the urea-containing mercaptosilane of the formula I.

For the substance of the formula IV HCl.H₂N—CH₂—CH₂—Cl, for example, the integral of the carbon atoms of the HCl.H₂N—CH₂—CH₂—Cl group (δ=41.25 ppm) or of the HCl.H₂N—CH₂—CH₂—Cl group (δ=40.79 ppm) is used for the determination of the relative contents.

The product prepared by the process according to the invention may have a residual content of isocyanatosilane of the formula V of less than 10 mol %, preferably less than 5 mol %, more preferably less than 1 mol %, very preferably less than 0.1 mol %.

The relative molar percentages of the isocyanatosilane of the formula V in the product within a range of >1 mol %, prepared by the process according to the invention, are determined in the ¹³C NMR by integration of the carbon atoms in the —NCO group of the isocyanatosilane of the formula V against the carbon atoms in the Si—CH₂— group of the urea-containing mercaptosilanes of the formula I.

For the substance of the formula V (EtO)₃Si—CH₂—CH₂—CH₂—NCO, for example, the integral of the carbon atoms of the —NCO group (δ122.22 ppm) is used for the determination of the relative contents within a range of >1 mol %.

The relative molar percentages of the isocyanatosilane of the formula V in the product within a range of <1 mol %, prepared by the process according to the invention, are determined by quantitative FT-IR spectroscopy known to those skilled in the art. The method is calibrated by using calibration solutions of suitable concentration (for example in C₂Cl₄). For the measurement, about 1 g sample is weighed into a 25 ml rollneck bottle, and 25 g of C₂Cl₄ are added. The sample is agitated on an agitator for 1-2 hours. Thereafter, the lower liquid phase is metered cautiously into a 20 mm IR cuvette and analysed by FT-IR spectroscopy (4000-1200 cm⁻¹, resolution 2 cm⁻¹). Under the same conditions, a spectrum of the solvent is recorded for subtraction.

For the substance of the formula V (EtO)₃Si—CH₂—CH₂—CH₂—NCO, for example, the wavelength of the valence vibration of the —NCO group at 2270 cm⁻¹ is used for the determination of the relative contents within a range of <1 mol %.

The product prepared by the process according to the invention may have a residual content of isocyanate-halogen compound of the formula VI of less than 25 mol %, preferably less than 10 mol %, more preferably less than 5 mol %, very preferably less than 3 mol %.

The relative molar percentages of the isocyanate-halogen compound of the formula VI in the product prepared by the process according to the invention are determined in the ¹³C NMR by integration of the carbon atoms in the OCN—CH₂— group of the isocyanate-halogen compound of the formula VI against the carbon atoms in the Si—CH₂— group of the urea-containing mercaptosilane of the formula I.

For the substance of the formula VI OCN—CH₂—CH₂—Cl, for example, the integral of the carbon atoms of the OCN—CH₂— group (δ=124.33 ppm) is used for the determination of the relative contents.

The product prepared by the process according to the invention may have a residual content of aminosilane of the formula VII of less than 10 mol %, preferably less than 5 mol %, more preferably less than 1 mol %, very preferably less than 0.1 mol %.

The relative molar percentages of the aminosilane of the formula VII in the product prepared by the process according to the invention are determined in the ¹³C NMR by integration of the carbon atoms in the —CH₂—NH₂ group of the aminosilane of the formula VII against the carbon atoms in the Si—CH₂— group of the urea-containing mercaptosilane of the formula I.

For the substance of the formula VII (EtO)₃Si—CH₂—CH₂—CH₂—NH₂, for example, the integral of the carbon atoms of the —CH₂—NH₂ group (δ=45.15 ppm) is used for the determination of the relative contents.

Urea-containing mercaptosilane of the formula I prepared by the process according to the invention can be characterized by a ¹H, ¹³C or ²⁹Si NMR method known to those skilled in the art.

The soluble fraction of the urea-containing mercaptosilane of the formula I in the products obtained by the processes according to the invention in DMSO-d⁶ or CDCl₃ is determined by adding an internal standard, for example triphenylphosphine oxide (TPPO), in DMSO-d6 or in CDCl₃, and a ¹H NMR method known to those skilled in the art.

The urea-containing mercaptosilanes of the formula I can be used as adhesion promoters between inorganic materials, for example

glass beads, glass shards, glass surfaces, glass fibres, or oxidic fillers, preferably silicas such as precipitated silicas and fumed silicas,

and organic polymers, for example thermosets, thermoplastics or elastomers, or as crosslinking agents and surface modifiers for oxidic surfaces.

The urea-containing mercaptosilanes of the formula I may be used as coupling reagents in filled rubber mixtures, examples being tyre treads, industrial rubber articles or footwear soles.

Advantages of the inventive urea-containing mercaptosilanes of the formula I are improved processing characteristics, network density, wet skid properties and dynamic stiffness in rubber mixtures.

EXAMPLES Comparative Example 1 Preparation of (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—SH from (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—Cl and NaSH

To a solution of NaSH in ethanol [prepared by introducing H₂S (15.21 g, 0.45 mol, 1.07 eq) into a sodium ethoxide solution (prepared from Na (10.55 g, 0.46 mol, 1.10 eq) in EtOH (300 mL))] is added, by metered addition at 52° C., (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—Cl (138.90 g, 0.42 mol, 1.00 eq) in ethanol (300 ml), and the mixture is heated to 78° C. After a reaction time of 5 h, the mixture is cooled to room temperature and the suspension is filtered. The filtrate is freed of the solvent on a rotary evaporator and dried under reduced pressure. The (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—SH product (134.96 g, 97.9% of theory) is obtained as a white solid.

¹H NMR (δ_(ppm), 500 MHz, CDCl₃): 0.64 (2H, t), 1.23 (9H, t), 1.36 (1H, br), 1.61 (2H, m), 2.67 (2H, t), 3.17 (2H, m), 3.37 (2H, m), 3.81 (6H, q), 4.74 (1H, br), 4.94 (1H, br); ¹³C NMR (δ_(ppm), 125 MHz, CDCl₃): 7.8 (1C), 18.3 (3C), 23.8 (1C), 25.6 (1C), 43.0 (1C), 43.5 (1C), 58.4 (3C), 158.9 (1C).

Example 1 Preparation of (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CO—CH₃ from (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—Cl and KSAc

(EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—Cl (81.52 g, 0.25 mol, 1.00 eq) is initially charged in ethanol (85 ml) in a 500 ml three-neck flask with stirrer, reflux condenser and internal thermometer. Potassium thioacetate (28.48 g, 0.25 mol, 1.00 eq) is added and the mixture is heated to reflux. After a reaction time of 3.5 h, the mixture is cooled to room temperature and the suspension is filtered. The filtrate is freed of the solvent on a rotary evaporator and dried under reduced pressure. The (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CH₃ product (81.64 g, 89% of theory) is obtained as a light brown solid.

¹H NMR (δ_(ppm), 500 MHz, CDCl₃): 0.64 (2H, t), 1.24 (9H, t), 1.61 (2H, m), 2.35 (3H, s), 3.01 (2H, t), 3.16 (2H, t), 3.34 (2H, t), 3.82 (6H, q), 4.5-7.0 (2H, br); ¹³C NMR (δ_(ppm), 125 MHz, CDCl₃): 7.8 (1C), 18.3 (3C), 23.8 (1C), 29.9 (1C), 30.6 (1C), 40.0 (1C), 43.0 (1C), 58.4 (3C), 159.0 (1C), 195.8 (1C).

Example 2 Preparation of (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CO—CH₃ from (EtO)₃Si—CH₂CH₂CH₂—NH₂, OCN—CH₂CH₂—Cl and KSAc

3-Aminopropyltriethoxysilane (132.82 g, 0.60 mol, 1.00 eq) is initially charged in ethanol (300 ml) in a three-neck flask with precision glass stirrer, internal thermometer, dropping funnel and reflux condenser, and cooled to −78° C. 2-Chloroethyl isocyanate (63.34 g, 0.60 mol, 1.00 eq) is added dropwise at −78 to −68° C. within 1.75 h and then the mixture is heated to 50° C. Potassium thioacetate (68.53 g, 0.60 mol, 1.00 eq) is added in five portions and the mixture is heated to reflux. After a reaction time of 2.25 h, the mixture is cooled to room temperature and the suspension is filtered. The filtrate is freed of the solvent on a rotary evaporator and dried under reduced pressure. The (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CH₃ product (213.91 g, 97.3% of theory) is obtained as a waxy white solid.

¹H NMR (δ_(ppm), 500 MHz, CDCl₃): 0.64 (2H, t), 1.22 (9H, t), 1.62 (2H, m), 2.35 (3H, s), 3.01 (2H, t), 3.16 (2H, t), 3.34 (2H, t), 3.82 (6H, q), 4.7-5.0 (2H, br); ¹³C NMR (δ_(ppm), 125 MHz, CDCl₃): 7.8 (1C), 18.3 (3C), 23.8 (1C), 29.9 (1C), 30.6 (1C), 40.1 (1C), 43.0 (1C), 58.4 (3C), 158.7 (1C), 195.9 (1C).

Example 3 Preparation of (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CH₃ from (EtO)₃Si—CH₂CH₂CH₂—NCO, HCl.H₂N—CH₂CH₂—Cl and KSAc

2-Chloroethylamine hydrochloride (73.86 g, 0.70 mol, 1.00 eq) is initially charged in ethanol (2.0 l) in a 4 l three-neck flask with precision glass stirrer, internal thermometer, dropping funnel and reflux condenser, and cooled to −78° C., and sodium ethoxide (226.83 g, 0.70 mol, 1.00 eq, 21% in ethanol) is added. 3-Isocyanatopropyl(triethoxysilane) (173.15 g, 0.70 mol, 1.00 eq) is then added dropwise at −78 to −65° C. within 3 h and then the mixture is heated to 50° C. Potassium thioacetate (79.95 g, 0.70 mol, 1.00 eq) is added in five portions and the mixture is heated to reflux. After a reaction time of 4 h, the mixture is cooled to room temperature and the suspension is filtered. The filtrate is freed of the solvent on a rotary evaporator and dried under reduced pressure. The (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—CH₂CH₃ product (288.02 g, quant.) is obtained as an orange oil.

Example 4 Rubber Mixtures

The formulation used for the rubber mixtures is specified in Table 1 below. In this table, the unit phr means parts by weight based on 100 parts by weight of the raw rubber used. The inventive silane is used in isomolar amounts relative to the comparative silane.

TABLE 1 Amount [phr] Amount [phr] Ref. rubber mixture I Rubber mixture II Substance comprising Comp. Ex. 1 comprising Inv. Example 2 1st stage NR TSR^(a) 10 10 BR^(b) 18 18 SSBR^(c) 72 72 Silica^(d) 95 95 ZnO 2.5 2.5 Stearic acid 2.5 2.5 TDAE oil 50 50 Antiozonant wax 2 2 6PPD^(e) 2 2 Comp. Example 1 12 — Example 2 — 14 2nd stage Batch Stage 2 DPG^(f) 2 2 CBS^(g) 2 2 Sulphur 2 2 Substances used: ^(a)NR TSR: SIR 20 SED, from Aneka Bumi Pratama (TSR = Technically Specified Rubber; SIR = Standard Indonesian Rubber) ^(b)BR: polybutadiene, Europrene Neocis BR 40, from Polimeri ^(c)SSBR: Sprintan ® SLR-4601, from Styron ^(d)silica: ULTRASIL ® VN3 GR, from Evonik Industries AG ^(e)6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine ^(f)DPG: diphenylguanidine ^(g)CBS: N-cyclohexyl-2-benzothiazolesulphenamide

The mixture was produced under customary conditions in two stages in a laboratory kneader for production of rubber mixtures (volume 300 milliliters to 3 liters), by first mixing, in the first mixing stage (base mixing stage), all the constituents apart from the vulcanization system (sulphur and vulcanization-influencing substances) at 145 to 165° C., target temperatures of 152 to 157° C., for 200 to 600 seconds. Addition of the vulcanization system in the second stage (ready-mix stage) produces the finished mixture, with mixing at 90 to 120° C. for 180 to 300 seconds.

The general process for producing rubber mixtures and vulcanizates thereof is described in “Rubber Technology Handbook”, W. Hofmann, Hanser Verlag 1994.

The rubber testing is effected by the test methods specified in Table 2.

TABLE 2 Physical testing Standard/conditions Moving die rheometer (rotorless vulcameter): ISO 6502 Minimum torque (dNm) ASTM D5289-12 Torque difference: maximum torque − minimum torque (dNm) Rebound resilience at 23° C. (%) DIN 53512 Dynamic/mechanical analysis at 55° C. ISO 4664-1 Dynamic storage modulus E′ at 0.15% elongation and at 8% elongation (MPa)

The mixtures were used to produce test specimens by vulcanization under pressure at 160° C. after t₉₅ (measured on a moving die rheometer to ISO 6502/ASTM D5289-12). Table 3 reports the rubber data for the vulcanizates.

TABLE 3 Ref. rubber Rubber mixture I mixture II comprising comprising Substance Comp. Ex. 1 Inv. Ex. 2 Raw mixture results: Moving die method: minimum torque 4.4 3.5 after 3rd stage [dNm] Moving die method: Torque difference: 12 18 maximum torque − minimum torque (dNm) after 3rd stage Vulcanizate results: Rebound resilience 23° C. [%] 29 26 Dynamic/mechanical analysis at 55° C. 10.1 16.5 E′ at 0.15% elongation (MPa) Dynamic/mechanical analysis at 55° C. 6.0 7.1 E′ at 8% elongation (MPa) Dynamic/mechanical analysis at 55° C. 4.1 9.4 E′ at 8% elongation - E′ at 0.15% elongation (MPa)

Rubber mixture II comprising the inventive urea-containing mercaptosilane from Example 2 shows improved processing characteristics (lower minimum torque after the 3rd mixing stage), increased network density (greater difference of maximum torque—minimum torque), improved wet skid properties (rebound resilience at 23° C.) and increased dynamic stiffness (E′ at 0.15% elongation, E′ at 8% elongation, and E′ at 8% elongation—E′ at 0.15% elongation) compared to reference rubber mixture I comprising Comparative Example 1 (urea-containing mercaptosilane) used in isomolar amounts. 

What is claimed is:
 1. A urea-containing mercaptosilane of formula I

where each R¹ is independently selected from the group consisting of a C1-C10 alkoxy group, a C2-C10 cyclic dialkoxy group, a phenoxy group, a C4-C10 cycloalkoxy group, a C6-C20 aryl group, a C1-C10 alkyl group, a C2-C20 alkenyl group, a C7-C20 aralkyl group or a halogen, R² is a monovalent C1-C20 hydrocarbon group and each R is independently a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group.
 2. The urea-containing mercaptosilane according to claim 1, wherein the urea-containing mercaptosilane is (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—CH₃, (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃, (CH₃CH₂O)₃Si—CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃ or (CH₃CH₂O)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂CH₂—S—C(O)—(CH₂)₆CH₃.
 3. The urea-containing mercaptosilane according to claim 1, wherein the urea-containing mercaptosilane is (EtO)₃Si—CH₂CH₂CH₂—NH—CO—NH—CH₂CH₂—S—C(O)—CH₃.
 4. A process for preparing the urea-containing mercaptosilane of claim 1, comprising reacting in an alcohol a halosilane of formula II

with a compound of formula III

where R¹, R² and R are each as defined in claim 1, Hal is F, Cl, Br or I and M is an alkali metal.
 5. The process of claim 4, wherein the reaction is conducted under a protective gas atmosphere.
 6. The process of claim 4, wherein the reaction is conducted at temperatures between 0° C. and 150° C.
 7. The process of claim 4, wherein the alcohol is ethanol.
 8. The process of claim 4, wherein the halosilane of formula II is prepared by adding a base to a hydrochloride salt of an amine of formula IV

and an isocyanatosilane of formula V

where Hal, R¹ and R are each as defined in claim
 4. 9. The process of claim 8, wherein the base is NaOEt.
 10. The process of claim 4, wherein the halosilane of formula II is prepared from an isocyanate-halogen compound of formula VI

and an aminosilane of formula VII

where Hal, R and R¹ are each as defined in claim
 4. 11. The process of claim 10, wherein the reaction is conducted in ethanol.
 12. The process of claim 4, wherein the ethanol is distilled off.
 13. The process of Process for preparing urea-containing mercaptosilane of the formula I according to claim 12, wherein a product obtained from the reaction is dried. 